468
FXUS65 KTFX 310253
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
853 PM MDT Sat Aug 30 2025

.KEY MESSAGES...

 - Isolated to widely scattered showers and thunderstorms will
   remain possible through the early evening hours, with overall
   dry conditions then expected through early next week.

 - Patchy fog will once again be possible, especially in the Milk
   River Valley in North Central Montana.

 - Near to above normal temperatures are expected through the next
   week.

&&

.UPDATE...

Isolated shower and thunderstorm activity over the eastern
portions of North-central Montana continues to diminish with the
loss of diurnal heating; however, there is one cluster of showers
and storms moving east southeast through northern/central Fergus
County that may linger through midnight or so. The current
mesoanalysis still shows some surface CAPE on the order of 500 to
1,000 J/kg, but CIN should ultimately win out given the
aforementioned loss of heating. Regardless, this area of
convection will produce cloud to ground lightning, gusty winds up
to around 30 to 35 mph, and brief downpours until it dissipates.
Otherwise, the primary concern will be patchy fog late tonight
into Sunday morning, mostly over the Milk River Valley. - RCG

&&

.DISCUSSION...
/Issued 225 PM MDT Sat Aug 30 2025/

 - Meteorological Overview:

Upper level ridge will build in over the Northern Rockies through
the first half of the upcoming work week, which will allow
temperatures to warm above normal across all locations. Winds will be
light and variable beneath the ridging pattern with overall dry
conditions. By Tuesday an upper level trough and associated closed
low will begin to to dig south and east to over the Great Lakes.
This digging trough will help narrow the upper level ridge over the
Northern Rockies through Wednesday and shift the ridge axis further
west, resulting in increasing northwest flow aloft over North
Central through Southwest Montana through Thursday. Near normal
temperatures and overall dry conditions are expected beneath this
northwest flow pattern; however, an isolated shower or storm can`t
be ruled out from Tuesday through Thursday. Upper level trough over
the Eastern Pacific will begin to move towards the western seaboard
through the end of the work week and weekend, which will lead to the
breakdown and flattening of the upper level ridge over the Northern
Rockies. This ridge breakdown and flattening of the ridge will lead
to increasing southwest to west surface winds and increasing
precipitation chances. - Moldan

 - Forecast Confidence & Scenarios:

Patchy Dense Fog Tonight/Sunday Morning :

Hi-Res Ensemble Forecast (HREF) guidance supports another night
for reduced visibilities over portions of the Central and North
Central Montana plains due to fog, most notably in Hill and
Blaine Counties. While the probability for visibilities less than
1/4 mile or less is low across these areas, generally around a
5-10%, recent precipitation, clear skies, and light easterly winds
through the Milk River Valley would support the potential for
patchy dense fog developing. - Moldan

&&

.AVIATION...
31/00Z TAF Period

An area of isolated showers and an occasional rumble of thunder
over North-central Montana will slowly drift off to the
east/southeast through 31/04Z before dissipating. This activity
should stay in between terminals, but a stray evening shower or
storm can`t be ruled out for KHVR or KLWT. Later tonight, patchy
fog is expected to develop along the Hi-Line, most widespread in
the Milk River Valley area between 31/09 and 31/15Z. The mention
of fog was left out of KCTB due to overnight light westerly winds
and only a VCFG was added to KHVR for now given low probabilities
(<20%) for impactful visibility reductions. Otherwise VFR
conditions are expected outside of some smoke and haze aloft
compromising slantwise visibility in Southwest Montana at times.
- RCG


Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  52  88  51  88 /  10   0   0   0
CTB  49  85  48  87 /  10   0   0   0
HLN  52  86  53  88 /   0   0   0   0
BZN  47  84  48  86 /   0   0   0   0
WYS  34  76  35  79 /  10   0   0   0
DLN  44  80  45  83 /   0   0   0   0
HVR  51  86  53  87 /  20   0   0   0
LWT  50  83  51  83 /  20   0   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$
http://www.weather.gov/greatfalls